Turbine rotor



Aug. 22, 1944. u. MEININGHAUS 2,356,605

r TURBINE ROTOR Filed Jan. 15, 1941 2 Sheets-Sheet 2' 1% J1 J2 J3 J4 J5 J0 l'rzvenlov: 042/01 Mn/w/ve/mus Patented Aug. 22, 1944 TURBINE ROTOR Ulrich Meininghaus, Mulheim on the Ruhr, Germany; vested in the Alien Property Custodian Application January 3, 1941, Serial No. 373,008 In Germany January 8, 1940 10 Claims.

The present invention relates to the construction of rotors carrying blades for axial flow rotary machines, and especially for steam and gas turbines.

It is the general object of the invention to provide an improved rotor for axial flow engines which is capable of running with a high number of revolutions per minute without showing any noticeable critical speed over the total actually used range of speed, and in particular a rotor which is easy to manufacture from parts kept in storage and formed to give a high resistance to centrifugal forces and which, accordingly, is built up of a plurality of single discs with axially extending, rims. Other, more specific objects ofthe invention will appear from the detailed description hereinafter. I

The accompanying drawings illustrate by way of example difierent'embodiments of the invention. Fig. 1 presents a vertical section through a steam turbine with a rotor according to the invention; Fig. 2 shows on an enlarged scale a section through a part of the rim of the rotor with a cylindrical ring inside of the rims of two adjacent discs; Fig. 3 shows the same section with a conical ring inside of the rims of two adjacent discs; Figs. 4 and 5 show the same section with a conical ring between the rims of two adjacent discs; Fig. 6 illustrates a rotor wherein the rims of adjacent discs are welded together and Figs. 7 and 8 show in detail the way of supporting the hubs of these discs on the shaft; Fig. 9 is an enlarged detail, similar to Fig. 8, showing means for securing the hubs'on the shaft; Fig. 10 is an enlarged transverse section showing the securing means.

In Fig. 1 the steam enters the turbine housing I at 2, impinges the Curtis-blading 3 and flows then through the reaction blading 4, leaving the housing at 5. 0n the shaft 6 which is supported in the bearings I the discs 8-l5 are shrunk. At the same time the rim of the disc 9 is rigidly supported in radial direction against the rim of the disc 8, the rim of the disc l0 against the rim of the disc 9 and so on. This support of for gliding in axial direction so that any diiferenthe rims against each other in radial direction prevents any radial displacement of the rims relative to each other and therewith any radial displacement of the adjacent hubs l6 and of the difierent sections of the shaft 6 on which the hubs l6 are shrunk. In this way the shaft 6 is stiffened in a way that raises the critical speed of the shaft considerably. In fact, the rotor construction as shown provides for higher critical speeds than heretofore known constructions.

Compared with a rotor wrought of one piece of steel the total weight as one factor determining the critical speed is considerably reduced, the shaft ends being just as rigidly connected to the whole assembly. Compared with a rotor welded together of single discs without centre bore the total weight is the same, but the shaft ends are more rigidly connected to the whole assembly then the two stub ends which are in direct connection with the end discs only.

The stiffness of the rotor will be further increased when the rims of adjacent wheels are additionally supported against each other in axial direction. For instance, the rims of adjacent discs may be welded together as shown in Fig. 6. This may be done if the temporary difference in expansion between the rims and the shaft is taken up by axial gliding of the support between the hubs and the shaft. But dampening any relative lateral movement of the rims of adjacent discs will in general be sufficient; The construction of Fig. 2 provides a supportof the rims of adjacent discs in radial direction which allows tial expansion of the rims as compared with the expansion of the shaft may be taken up by the rim support. This axially gliding support of the rims is effected by a ring I! arranged inside of the rims l3 and I 4 and pressed with its cylindrical outer circumference against the inner cylindrical surfaces of the rims l3 and I4, thus providing a rigid connection between the hubs and the shaft. The radial pressure exerted by the ring I! is determined for the main part by the centrifugal force acting on the ring according to the chosen relation of the radial thickness of the ring wall to the mean ring radius. Additionally, the ring may be pressed or shrunk into the rims without increasing the radial pressure considerably on account of the high elasticity of such thin walled rings. The radial pressure may, therefore, be determined practically independently of small deviations in the fit. This is a great advantage compared with the rotor construction shown in Fig. l. The friction damping lateral movements of the rims will be comparatively small, constant and equally distributed on the circumference, thus practically eliminating additional bending forces on the shaft in case of differential expansion of the rims. According to this part of the invention a comparatively small friction will suffice to prevent temporarily rela; tive lateral movements of. adjacent rims and thus allow for safely going through a critical speed. Thus the first 'tical speed may be chosen below the normal running speed of the rotor and will notwithstanding not affect the starting and stopping of the turbine. In this way the advantages of actually running above the first critical speed are made use of while at the same time eliminating the disadvantages,

In the construction of Fig. 3 the outer circumference of the rings I1 is provided with conical surfaces which press against corresponding conical surfaces of the rims I91 and M. This construction facilitates the mounting of the rings ll if these rings are inserted with some initial radial ressure to insure a tight fit under all conditions. At the same time it makes it pos-' sible to increase the resistance against gliding of the rings I1 against the rims l3 and I4 and thus to prevent any gliding which may be caused continuously during each revolution by the slight bending of the horizontal shaft due to the weight imposed on it. The friction should go be such that gliding of the ring ll against the rims l3 and It should occur only if a differential expansion between the rims and the shaft has to be equalized.

If the slant of the conical surfaces of ring I! is increased as shown in Fig. 4 the rings II will be positioned between the rims of. the adjacent discs. To secure an absolute centric position of the ring l1 it is held in position by an elastic wall is and an elastic ring l9 which is fastened 5 to one of the discs by means of a caulking wire 20. The one end of the ring ll may even press against the rim l4 with a radial surface'if only the other end presses against the rim l3 with an inclined surface according to Fig. 5. The

ring I! must only have a smaller axial thickness at the outer circumference than at the inner circumference. Means for securing the relative centric position of ring i1 and the rim H are then indispensable but simpler. One elastic ring 2| is sufficient. With the increased slant the ring I] is now positioned between the rims l3 and I4. The slant surfaces and the elastic connection between ring and rim will still support the rims against each other in radial direction, but at the same time in axial direction. At the same time the ring II will allow for relative axial moveagainst the steam by means of projections 22 and 23 and recesses 24 and 25 cut into the rims to decrease the transfer of heat. But the rings H are easily compressed by small axial forces and will easily expand by centrifugal ,force if the total axial length of rims plus rings does not co- 0 incide with the length of the corresponding shaft section. The rings ll will during all movements keep the axial distance between the rims equal along the whole circumference thus enforcing absolute parallelity of the Thus the rotor is free to expand axially but at the same time is stiffened against any bending. lnthis way the critical speed is actually raised.

A perfect stiffness of the total rotor is attainable by welding together the adjacent rims as o shown in Fig. 6. It is then necessary to provide for a support between the hubs of the discs and the shaft which allows for axialgliding and yet keeps the centre of the shaft in line with the centres of the wheel hubs under all conditions.

The 5 2 assaeos cesses 29 of the hub I6 while the teeth 29 of the hub 16 mesh in the same way with recesses 30 of the bush 29.

As shown in Figs. 9 and 10 it will be easier to ensure a tight fit. between the teeth 21 and the gaps 28 as well as between the teeth 29 andthe gaps 39 if the teeth 29 are split in the centre by slots 3|. Wedges 32 and 33 may then be driveninto these slots 3| to drive the halves of the teeth 29 apart and bring them to a close fit with the side walls of the gaps 39. The process of manufacturing the teeth is simplified because the thickness of the teeth and the width of the slots may differ to some extent before the teeth are driven apart. Slots 34 will make the bending of one-half of the teeth 29 easier. To ensure absolutely rigid connection between the parts, the half of the teeth 29 transferring the torque is left rigid against bending. As three surfaces will always come in touch with the corresponding surfaces of the gaps 39 it is my preferred construction to employ three rigid halves of teeth 29 only.

I claim:

1. A blade carrying rotor for axal fiow rotary machines, in particular steam or gas turbines, comprising a plurality of individual discs having axially extending rims relatively spaced to provide intervening spaces therebetween and hollow hubs, a shaft extending through said hubs, and means for bridging said intervening spaces for effecting interlocking of the rims of adjacent discs, whereby the hubs of adjacent discs are centered on the shaft and the mutual centering of the rims maintained during the operation of the rotor.

2. A rotor according to claim 1, wherein said shaft is supported rigidly in radial direction against the hubs of at least three discs.

3. A bladecarrying rotor for axial fiow rotary machines, in particular steam or gas turbines, comprising a plurality of individual discs having axially extending rims relatively spaced to provide intervening spaces therebetween hollow hubs, and a shaft extending through said hubs and being closely fitted therein, and means for bridging said intervening spaces to secure the rims of adjacent discs with reference to each other and thereby securing said hubs with reference to said shaft rigidly in radial direction so as to prevent any radial displacement in their position relative to each other.

4. A rotor according to claim 3, wherein the rims extend axially beyond the adjacent sides of the discs to provide overhanging undersurfaces, and wherein said means comprise central rings pressing with their cylindrical or substantially cylindrical outer circumferences against the inner surfaces of the rims of adjacent discs. 5. A rotor according to claim 3, wherein the rims extend axially beyond the adjacent sides of the discs to provide overhanging undersurfaces, and wherein said means comprise central rings of smaller radial thickness than the rims pressing with their cylindrical or substantially cylindrical outer circumferences against the inner surfaces of the rims of adjacent discs.

6. A rotor according to claim 3, wherein the rims extend axially beyond the adjacent sides of the discs to provide overhanging undersurfaces, and wherein said means comprise central perforated rings pressing with their cylindrical or 9. A rotor according to claim 3, including centrically supported rings arranged between the rims of adjacent discs, said rings being of smaller axial extension at the outer diameter than at the inner diameter and pressing with their end surfaces against surfaces of the rims with corresponding obliquity.

10. A rotor according to claim 3, wherein the rims have inner conical surfaces and including central rings having conical outer circumferences and pressing with such conical outer circumi'erences against the inner conical surfaces of the rims of adjacent discs.

- ULRICH MEININGHAUS. 

